Amplifier



Feb. 24, 1925. 1,527,654

E. W. KELLOGG ET AL AMPLI FIER Filed new 21. 1920 Irv/enters I Frank Elder", by J/i r/ Their- Attorhey Patented Feb. 2 4, 1925.

UNITED STATES 1,527,654 PATENT OFFICE.

EDWARD W. KELLOGG AND FRANK ELDER, F SCHENECTADY, NEW YORK, ASSIGNOTRS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

AMPLIFIER.

Application filed December 21, 1920. Serial No, 432,335.

To all whom it may concern:

I Be it known that we, EDWARD W. KnLLooo and FRANK ELDER, citizens of the United States, residing at Schenectady, in the.

5 county of Schenectady, State of New York,

have invented certain new and useful Improvements in Amplifiers, of which the following is a specification.

Our present invention relates to electron discharge devices, and more particularly to the use of such devices as amplifiers.

The object of our invention is to provide a simple and eilicient apparatus for amplifying electrical variations.

In carrying our invention into effect We preferably employ an electron discharge device of the negative resistance type, such for example, as that commonly known as the dynatron, which is described by Albert 20 W. Hull in a paper published in the Pro ceedings of the Institute of Radio Engineers'for 1918, at page 5.

In the use of such devices it has been customary to impress currents or potentials to be amplified upon a circuit which includes the negative resistance of the device and to lead off from the same circuit the amplified currents or potentials. A disadvantage sometimes arises in using the device in this way, as for example, when it is desired to employ two or more amplifiers in series.

In this case there may be a reaction between the circuits of the amplifiers which will cause the system to oscillate continu- 36 ously. There is also an inherent tendency to the production of oscillations in any circuit containing a negative resistance of the type mentioned, and inductance, and it is sometimes difficult to overcome this tendency 40 in the circuits which have previously been employed.

A further object of our invention is to overcome the disadvantages mentioned as well as others which may be present, and

provide a circuit arrangement for negative resistance amplifiers of the type mentioned which will be efficient in its operation.

In carrying our invention into effect we make use of a characteristic of such devices which, while it has previously been known, has never been utilized. The characteristic here referred to is the fact that for every change in the current in the negative re sistance circuit there is a complementary change in the circuit between the cathode and anode of the device. In other words, every change in the current in the negative resistance is accompanied by a corresponding change in the opposite direction in the current between cathode and anode. In utilizing this characteristic the current or potential variations to be amplified are impressed upon a circuit'containing the negative resistance of the device and the amplified current or potential variations are led off from or utilized in the circuit between cathode and anode. In this way the output circuit of the device is separated from the input circuit and the natural tendency of the device to produce oscillations either when used singly or when two or more are'used in series may be eliminated.

Our invention will best be understood both as to its organization and method of operation by reference to the following description taken in connection with the accompanying drawing in which we have indicated diagrammatically one Way in which our invention may be carried into effect.

As indicated in the drawing," an electron discharge device 1 of the dynatron type is provided with the usual electron emitting cathode 2, anode 3, and third electrode 4. The source 5- furnishes the potential necessary for maintaining the anode 3 at a desired positive potential with respect to the cathode. The source 6 furnishes the potential necessary for adjusting the poten- -tial of the third electrode at such a value that the circuit between cathode and third electrode will have a negative resistance characteristic. The circuit between cathode and third electrode also includes a positive resistance 7, which is preferably of substan tially the same value as the negative re sistance of the device 1. The electrical variations to be amplified are supplied to A the circuit 2, 6, 7, 4., by means of a transformer 8, the secondary of which is connected to the terminals of resistance 7. When a variable current or potential is set up in the secondary of the transformer 8 corresponding amplified current variations will be produced in the circuit 2, 6, 7, 4:.- Complementary current variations of equal value will also be provided in the anode circuit 2, 3,5, and these-current variations may be supplied by a transformer 9 to. a.

int

, in case the system is used for amplifying audio frequency currents. In case the cur rents to be amplified are of a frequency] which is not audible any other Suitable device-may be associated with the circuit 2, 3, 9, 5, for producing a desired indication] of the amplified currents. In case it is de- .t.we'encathode and third electrode, means sired to employ twoor more amplifiers-in for supplying electrical variations to the series the transformer 9ama3Lserve as the. circuit between'cathode and third electrode,

input transformer of a second amplifier.

The arrangement which we have described is verystable in its operation since the resistance 7 absorbs all of the power supplied by the circuit 2, 6, 7, 4, and since the resis tance 7 may be made very large, large variationsinpotential may be produced in both circuits. WVith this arfihgement, it is also possible to use any inductance desired in the output circuit without causing any tendency toward the production of oscillations as the output circuit doesnot have a negative resistance characteristic over tire op erating range employed. It is also possible to construct dynatrons in which the current to anode and third electrode is independent of the anode voltage over a considerable range. By using a device having this characteristic it is possible touse a considerable amount of impedance in the anode circuit and thereby secure large voltage amplification.

lVhile we have described only one circuit arrangement and illustrated the use of our invention with only one particular form of negative resistance, it will be apparent to thoseskilled in the art that it is by no means limited to the precise application shown, but that numerous modifications both in the circuit arrangements and particular form of negative resistance device used may be made without departing from the scope of our invention as set forth in the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States, is

1. An electron discharge device 'compris-.

cathode and anode for utilizing current variations produced in that circuit.

2. An electron discharge device comprisinga cathode, an anode and a third electrode enclosed in an evacuated receptacle, sources of potential applied to said electrodes of plying electrical variations to the positive resistance device, and means associated with the circuit between cathode and anode for utilizing current variations produced in that circuit.

4. An electron discharge device comprising a cathode, an anode, and, a third electrode enclosed in an evacuated receptacle,- sources of potential applied to said electrodes of such values that the device has a working range over which the current fiow 109 from the cathode to the third electrode varies inversely as the potential applied thereto,

a positive resistance device in the circuit between cathode and third electrode, the

. positive resistance of said device having approximately the'same value as the negative resistance of the circuit, means for supplying electrical variations to the circuit be- ,tween cathode and third electrode, and

means associated with the circuit between 110 cathode and anode for utilizing current variations produced in that circuit.

5. An electron discharge device comprising a cathode, an anode, and a third electrode enclosed in an evacuated rece tacle, V

sources of potential applied to sai electrodes of such values that the device has a I working range over which'the current flow from the cathode to the third electrode varies inversely as the potential applied n thereto and the current between cathode and anode varies in the opposite manner substantially independent of the potential of the anode, a positive resistance. device in, the circuit betweencathode and third electrode, the positive resistance 'of'said device having approximately the same valueas the negative resistance of the circuit, means for v7 supplying electrical variations to the circuit 1 between cathode and third electrode, and

means associated with the circuit between cathode and anode for utilizing current variations produced in that circuit.

6. An electron discharge device comprising a cathode, an anode and a third elecvaries inversely as the potential applied thereto, a positive resistance device in the circuit between cathode and third electrode,

means for supplyingelectrical variations to the positive resistance device, the positive resistance of said device having approximately the same value as the negative resistance of the circuit, and means associated with the circuit between cathode and anode for utilizing current variations produced in that circuit.

7 The method of operating an electron discharge device comprising an electron emitting cathode, an anode and a third electrode enclosed in an evacuated receptacle and having circuit connections between the cathode and each of the other electrodes, which consists in producing an emission of secondary electrons from the third electrode sufiicient to give the device a negative resistance characteristic, applying currents to be amplified to the circuit between cathode and third electrode and producing an indication of the resulting currents produced in the circuit between cathode and anode.

8. The method of operating an electron emitting cathode, an anode and a third electrode enclosed in an evacuated receptacle and having circuit connections between the cathode and each of the other electrodes the circuit connection between cathode and third electrode including a positive resistance,

which consists in'producing an emission of secondary electrons from the third electrode sufiicient to give the device a negative resistance in the circuit between cathode and third electrode approximately equal to the value of the positive resistance in the circuit, applying currents to be amplified to the circuit between cathode and thlrd electrode and producing an indication of the resulting currents produced in the circuit between cathode and anode. I 1

9. The method of operating an electron discharge device comprising an electron emitting cathode, an anode and a third electrode enclosed in an evacuated receptacle and having circuit connections between the cathode and each of the other electrodes, the circuit connection between cathode and third electrode including a positive resistance which consists in producing an emission of secondary electrons from the third electrode sufiicient to give the device a negative resistance in the circuit between cathode and third electrode approximately equal to the value of the positive resistance in the circuit, applying currents to be amplified to the positive resistance, and producing an indication of the resulting currents produced in the circuit between cathode and anode.

In witness whereof, we have hereto set -our hands this 20th day of December 1920. I discharge device comprising an electron 

